Updated

Medical officials say an extremely rare infection has been passed from an organ donor to at least one recipient in what is thought to be the first such transfer of the amoeba.

University of Mississippi Medical Center officials announced Friday that four people in three states received organs from a patient who died in November after having neurological problems. They would not say which states.

Dave Daigle, spokesman for the Centers for Disease Controls and Prevention, says two of the recipients are critically ill, but the others haven't shown symptoms.

Doctors say they test for known harmful diseases in organ donors, but there's no way to test for every possible ailment.